...I have not rebelled,The second reading destroys Martin Luther [and the protestant heresy*], and in his [their] own terms. The self proclaimed theological claim of rightness and superiority against catholicism is — justification [salvation] by faith alone, with a corollary that ‘works’ are meaningless. Luther also claimed only Scripture could change his mind, ‘sola scriptura’; and by that rationale his programme is demolished. Protestant theology stands on feet of clay.
have not turned back.
I gave my back to those who beat me,
...I am not disgraced;
...I shall not be put to shame.
...if anyone wishes to oppose me,
let us appear together.
Who disputes my right?
Let that man confront me.
See, the Lord GOD is my help;
who will prove me wrong?—Isaias l.5-9a (abbreviated)
What good is it, my brothers and sisters,
if someone says he has faith but does not have works?
Can that faith save him?
If a brother or sister has nothing to wear
and has no food for the day,
and one of you says to them,
“Go in peace, keep warm, and eat well, ”
but you do not give them the necessities of the body,
what good is it?
So also faith of itself,
if it does not have works, is dead.
Indeed someone might say,
“You have faith and I have works.”
Demonstrate your faith to me without works,
and I will demonstrate my faith to you from my works.
—James ii.14-18. NAB
The Gospel reading, from Mark viii, has Peter recognising that Jesus is the Christ [Messias], and then refers back to Isaias, in that of the suffering Jesus would undergo. Wavering, fearful but perceptive [Simon] Peter can see the true importance of Jesus.
*To some this is a minor point to start a schism an heresy—faith not works, instead of faith and works. For faith does not exclude good works. The false dichotomy of faith OR works is partially a non-sequitar, and a straw man argument.